[clang] [llvm] [SPIRV] Add support for the `SPV_EXT_long_vector` extension (PR #210279)

[Juan Manuel Martinez Caamaño via cfe-commits]

https://github.com/jmmartinez commented:

Just left a minor comment; I've skimmed over it and overall it looks good. I'll read it in depth later.

https://github.com/llvm/llvm-project/pull/210279